This patch, extracted from a larger change on gomp-4_0-branch, expands
a comment documenting struct switchstr in gcc.c.

2015-08-25  Thomas Schwinge  <thomas@codesourcery.com>
	    Joseph Myers  <joseph@codesourcery.com>

	* gcc.c (struct switchstr): Expand comment.

Co-Authored-By: Joseph Myers <joseph@codesourcery.com>

From-SVN: r227173